Is it a gimmick or a useful feature? Only you can decide but ControlAir, a free app for Mac OS X (10.10 or later) and available at the Mac App Store provides touch-free control over your media and entertainment apps.
It takes about 10 seconds to learn how to use it. And it works seamlessly up to five feet away from your Mac.
ControlAir lets you control apps like iTunes, the QuickTime Player, Netflix, Spotify, VLC, VOX and Rdio. To use just raise your index finger in front of your Mac's FaceTime camera. ControlAir presents a banner at the top of the screen with play/pause, skip/rewind and volume functions.
You move your finger from side-to-side to navigate and select the function you wish with an "air click." You can even mute by placing your finger to your lips.
Control Air does what it promises and does it well. I had fun playing with it at first, but after a couple of days found I wasn't using it any more. Your mileage may vary if your Mac isn't within reach and you're too lazy to get up and walk over to it. But, hey, it's free so you've nothing to lose by giving it a try.